The present invention relates to chairs and, more specifically, to an air pressure tube assembly for elevation adjustable seat stand, which has a simple structure and, is easy and inexpensive to manufacture.
Various air pressure-controlled elevation-adjustable seat stands are well known. Regular air pressure-controlled elevation-adjustable seat stands are commonly comprised of an air pressure tube assembly, which is composed of a big number of parts including barrel, top cap, inner tube, valve means, piston means, pin, bottom cap, and etc. These parts are commonly made of metal. These metal parts are commonly expensive, and their fabrication is complicated. Further, during operation of the air pressure tube assembly, air may leaks out of gaps between metal parts.
The present invention has been accomplished to provide an air pressure tube assembly for elevation-adjustable seat stand, which eliminates the aforesaid drawbacks. It is one object of the present invention to provide an air pressure tube assembly for elevation-adjustable seat stand, which is inexpensive to manufacture. It is another object of the present invention to provide an air pressure tube assembly for elevation-adjustable seat stand, which prevents air leakage. According to one aspect of the present invention, the air pressure tube assembly is comprised of a barrel, an inner tube mounted inside the barrel, a top cap mounted in one end of the barrel, a first valve and a second valve connected in a line between the top cap and the inner tube inside the barrel, a bottom cap fastened to one end of the inner tube remote from the top cap, a pin adapted to close/open the first valve and the second valve, a bolt fastened to the top cap and extended out of the barrel, and a piston assembly axially movably mounted in the inner tube, wherein the top cap, the first valve, the second valve, the inner tube and parts of the piston assembly are respectively injection-molded from plastics. According to another aspect of the present invention, small and big O-rings are installed in the top cap and the inner tube to seal gaps between the valves, the top cap, the inner tube, and the pin.